The present invention relates to an elastically damping device, particularly to a damping device which is applied to an engine mount for damping the vibration of the engine of a vehicle.
The elastically damping device generally comprises a first fluid chamber defined by a thick wall made of elastically deformable material, a second fluid chamber defined by a relatively thin wall made of elastically deformable material, a partition wall which separates the first fluid chamber and the second fluid chamber and an orifice which is formed in the partition wall so as to interconnect the first fluid chamber and the second fluid chamber. The damping device having the above structure is mounted on a body of a vehicle in the wall defining the first fluid chamber while supporting an engine.
The damping device of this type is required to be formed into a small size and a simple structure and to have an excellent vibration damping operation.
And the damping device is also required to have such a vibration damping effect as to increase in accordance with the increment of the amplitude of vibration.
Conventionally, a metallic plate provided with an orifice having a small diameter has been employed as the partition wall of the damping device.
However, the length of the flowing route of the orifice is small so that the flowing resistance generating in the orifice when the liquid passes the orifice is small. Therefore, sufficiently excellent damping effect cannot be obtained.
And the vibration damping effect does not increase in accordance with the increment of the amplitude of vibration.
In order to increase the flowing resistance of the orifice, it has been proposed to make the metallic partition wall thick and to make the length of the flowing route of the orifice large by forming the orifice into a spiral shape.
However, in the damping device having such a structure, as the thickness of the partition wall increases, the weight of the device also increases and the spiral orifice cannot be easily formed.
Furthermore, another damping device has been proposed in order to increase the flowing resistance of the orifice. In this damping device, the second fluid chamber is formed so as to arround the first fluid chamber, and the fluid chambers are separated from each other by a thick wall. An orifice is formed in the thick wall so as to extend in the lateral direction therethrough.
This device has a defect that the size thereof is large in the lateral direction.
In addition, this device has another defect that into the liquid filling the first and the second fluid chambers, air inevitably intermixes.
When the air having compressibility is mixed with the liquid filling the fluid chambers, particularly the first fluid chamber, the vibration damping effect of the device lowers.
Therefore, it is desirable that the air within the first fluid chamber easily moves into the second fluid chamber.
In the conventional device, the orifice is formed in the lateral direction of the device so that the air does not easily escape into the second fluid chamber.
Accordingly, one object of the present invention is to provide a simple and small sized elastically damping device having an excellent vibration damping effect.
Another object of the present invention is to provide an elastically damping device of which damping effect increases in accordance with the increment of the amplitude of vibration.
A still another object of the present invention is to provide an elastically damping device having such a construction that the air within the liquid easily gathers into the second fluid chamber.
A further object of the present invention is to provide an elastically damping device having excellent durability.
A still further object of the present invention is to provide an elastically damping device which can be easily assembled.